This invention relates to the monitoring of pyrometallurgical processes, and more particularly to the measurement of concentrations of major metallic species in molten metallurgical phases such as slags, mattes, bullions and impure or semi-refined molten metals.
It is already known to use electrolytic sensors in which a reference electrode is separated by a solid electrolyte from an electrode immersed in a melt and an e.m.f. is measured, to study the concentration trend of a minor element in the melt. Such a procedure is described for example in UK patent no. GB-A-1,470,558, which corresponds to U.S. Pat. No. 4,166,009.
One of the disadvantages associated with the use of such sensors is that the e.m.f. change is the same for a change from 1 part per million to 10 parts per million of the element being detected as it is for the change from 10,000 to 100,000 p.p.m. Such devices are therefore considerably less sensitive at higher concentrations of the element being detected.